The floating-point environment includes exception flags and masks, the
current rounding mode, and other architecture-specific settings.
However, it does not include the floating-point register file.

The
fegetenv
function stores the current floating-point environment in the object
pointed to by
envp,
whereas
feholdexcept
saves the current environment, then clears all exception flags
and masks all floating-point exceptions.

The
fesetenv
function restores a previously saved environment.
The
feupdateenv
function restores a saved environment as well, but it also
raises any exceptions that were set in the environment it
replaces.

The
feholdexcept
function is often used with
feupdateenv
or
fesetenv
to suppress spurious exceptions that occur as a result of
intermediate computations.
An example in
fenv(3)
demonstrates how to do this.